Psychrometer



May 29/ 1928.

1,671,103- E. J. CARROLL ET AL. I

PSYCHROMETER Filed June 14. 1922 I 00000 oooooooooooooooooooo o 0000 00000000 cwooHoooooo o \o o o o o o 0 c ooooooo 6000 A T TO/(NE Y.

Patented May 29, 1928.

UNITED STATES PATENT OFFICE.

EMIL J. CARROLL AND GEORGE W. JOHNSON,

AMERICAN LAUNDRY MACHINERY COMPANY, OF CINCINNATI, OHIO, A CORPOBA IION OF OHIO.

OF CINCINNATI, OHIO, ASSIGNORS TO THE PSYCHROMETER.

Application filed June 14, 1922. Serial No. 568,240.

This invention relates to psychrometers.

The object of the invention is to provide an improved psychrometer so arranged as to indicate relative humidity directly and without the use of specially prepared tables or the necessity of computation and also capable of use as-a controller to confinerelative humidity within predetermined maximum and minimum limits and so arranged as to enable the maximum and minimum limits to be readily varied byv a simple change in the instrument.

Other objects of the invention are in part in obvious and in part will appear more in detail hereinafter.

In the drawings Fig. 1 1s an elevation,

partly broken away and in section, of one form of instrument embodying the inven tion; Fig. 2 is an inverted sectional plan view on the line 22, Fig. 1, the front side of the instrument, indicated in Fig. 1, being shown at the top in Fig. 2; Fig. 3 is a detail sectional view illustrating one of the pairs of switches; and Fig. 4 is a diagrammatic view of the electric circuits.

Relative humidity is the degree of saturation or hygrometric state of the atmosphere and stated more specifically is the ratio of the amount of aqueous vapor in the atmosphere to the amount required to completely saturate it at the given temperature condition. This ratio' is usually determinable by various instruments, one common form of which includes wet and dry bulb thermometers from the temperature readings ,upon which, together with the reading of the barometer at the time, the pressure of the vapor in the airmay be determined by means of an empirical formula or more conveniently from specially prepared tables. In

'suchinstruments the relative humidity can only be determined by an inspection of the apparatus and subsequent calculation or a comparison of the readings with tables.

According to the present invention the instrument, technically termed is a psychrometer, is so constructed as to embody within its parts or mechanism all of the various factors in the empirical formula so that actuation of said instrument by the wet and dry bulb thermometersproduces a direct indication of relative humidity or some humidity controlling effect.

The. instrument shown in the drawingsration of which liquid at the bulb causes the wet bulb thermometer to register the evaporation point. Each of the thermometers is provided with a Bourdon tube, said tubes eing marked 9 and forming the connecting means by which the thermometers control the actuating or movable parts of the instrument. Each thermometer actuates a pair of switches, and as the switches actuated by the two thermometers are identical in form, construction and operation, description of one set of switches will suffice for both, except that hereafter where necessary, the parts on one side of the instrument will be called the dry parts and on the other side the wet parts.

Each Bourdon tube 9 terminates in a coiled portion 10 fastened at its far end to a bracket 11 supporting a stud 12 carrying the insulating sleeve 13 on which are su ported two switch arms, the first of which marked 14, is a maximum switch and the second of which, marked 15, is a minimum switch. Each of these switch arms is provided at its ends with an adjustable contact member 16, said contacts 16 being arranged during rotation of the switch arm to wipe in turn over a series of contacts 17 mounted in the wall "2 and spaced 'circumferentially about the axis of rotation of the switch arm.

The instrument therefore includes four such of the switch arms 14, 15 and to the outer ends of, which the circuit-wires are attached, as will hereafter appear.

The two pairs of switch arms extend from the sides of the instrument toward each other, and in the insulating; Wall 2, in the space between the neighboring ends of the pairs of switch arms, are located a second series of contacts 19, best shown in Fig. 2. These contacts are placed in four parallel rows, as shown in Fig. 1 and the contacts of the outer two rows are short, while the contacts of the inner two rows are long, enabling said contacts 19. row by row, to be individually connected by suitable wires to certain ones of the contacts of the corresponding four rows of contacts 17, as will be readily understood.

The front wall 3 of the instrument is provided with a recess in which the outer ends of the four rows of contacts 19 are exposed. Said recess is designed to receive any one of a series of plates provided with contacts and connections to cross connect various ones of the two inner rows of contacts 19 and to likewise cross connect various ones of the two outer rows of contacts 19, for specified maximum and InlIllmum (or vlce versa) percentages ofrelatlve humidity. as will more fully appear. This as the temperatures registered by the wet and dry bulb thermometers vary all four switches will move to and fro across their respective sets of 'circumferentially spaced contacts 17. The intention in the present instrument is to utilize the two switches 14,

one operated by the wet and the other by the dry bulb thermometer, as maximum relative humidity switches, and the-two shorter switch armsl5, one for each thermometer, as minimum relative humidity switches. Consider now the maximum switch 14 actuated by the dry bulb thermometer. Its pos tion always corresponds to the given dry bulb temperature condition-and it will stand at rest, at any given temperature, upon a selected one of itsrowof contacts 17. It is obvious that at this temperature the relative humidity may vary, because the empirical formula 'for relative humidity includes the reading of the wet bulb thermometer, the barometer reading etc. Consequently with the maximum humidity dry switch 14 at one position, the corresponding maximum humidity wet switch 14 Wlll occupy yarious positions depending upon the relative humidity. The same is true as to the various definite temperatures required or indicated between .the

by the two minimum relative humidity switches 15. The contacts 24 and '26 inthe plate 22 are so paired or cross connected as to produce proper co-relation or cooperaation between the pairs of maximum and minimum switches 14. 15 at any desired maximum and minimum percentages of relative humidity. For example, in the instru- .ment shown. the contacts 24 and 26 are paired or cross connected by wires 25, 27 to correspond to twenty percent minimum relative humidity and thirty percent maximum relative humidity.

Assume that the instrument is placed in a room in which it is desired that the maximum relative humidity shall not exceed thirty percent and shall not be reduced below twenty percent. The efiect of the tem-' perature in the room on the dry bulb and wet bulb thermometers causes the several switches 14, 15 to move to the proper positions with their contacts 16 engaging the proper contacts 17 If at any tlme one of the maximum dry switches 14 engages a given one of its contacts 17 at the same time that the corresponding maximum wet switch 14 engages a contact 11 which is so cross connected by wires 20, contacts 19 and 26 and wire 27 as to correspond with' thirty percent relative humidity, current will flow maximum brushes 17 and through an indicating lamp or relay indicated conventionally at X, Fig. 4. Likewise, when the two minimum switches 15 reach at the same time two contacts 17, corresponding to twenty percent relative humidity, current flows through the relayor indicating lamp Y, as shown in Fig. 4. These indicators X and Y may be colored lamps, for example, one red and the other green, so that when the maximum relative humidity reaches thirty percent the operator or attendant is warned to reduce humidity, while when the opposite or second lamp Y is illluminated, he is warned to increase humidity. This arrangement enables an. attendant to regulate the humidity within definite limits by starting or stopping a suitable device or devices for moistening or drying the atmosphere.- At the same time, the indicators X and Y can obviously be relays or other electric control devices arranged to automatically set into operation or stop the operation of suitable devices,

such as a drier or moisture producer, for automatically raising or lowering relative humidity.

' It is obvious from the foregoing that the instrument is operative to indicate or to produce some useful effect at any desired high or low points of relative humidity and is also so arranged that by substitutingvarious ones of a set of plates 22 it can be made to indicate or operate at any desired maximum or minimum percentages of relative humidity. For example, the plate shown in the drawings is arranged to confine humidity between twenty and thirty percent. Another similar plate will have its contacts 24, 26 paired or cross connected by wires 25, 27, to confine humidity between twenty and twenty-five percent; another between twenty and forty percent, and still others between ten and thirty percent, fifteen and thirty percent, twenty-five and thirty percent and so on. g

An unlimited number of such plates can be provided with any two maximum and minimum percentages. By choosing the proper plate the relative humidity can be confined as narrowly orpermittcd to vary as widely as desired.

It is also obvious that the instrument may serve as a directindicator of relative humidity. At any time a series of plates, each suitably marked with the percentage or percentages of relative humidity which it represents can be inserted one by one into the instrument until one is found which produces a complete through circuit and results in an indicating effect.

The apparatus described is capable of extremely wide use, not only as a scientific instrument for determining and indicating relative humidity, but also as an indicator of maximum and minimum relative humidity and as an automatic controller of apparatus for varying relative humidity in any space or in any mechanism. It can be used for varying the humidity in show cases, chambers or rooms containing cigars or other substances or materials, or may also be used with drying or moistening machines to limit or vary the drying or moistening effect therein.

What we claim is:

1. A psychrometric instrument, comprising dry bulb and wet bulb thermometers. two electric circuits, and means controlled by said thermometers for producing a changed condition in one of said circuits when the relative humidity reaches a/predetermined maximum ratio and in the other of said circuits when the relative humidity reaches a predetermined minimum ratio, said means including variable means adapted by variation thereof to produce said changed conditions in said circuits when the relative humidity reaches any desired predetermined maximum and minimum ratios.

2. A psychrometric instrument, comprising dry bulb .and wet bulb thermometers, a switch controlled by each of said thermometcrs, an electric circuit including said switches, and contacts and conducting means connecting said switches to produce a changed condition in said circuit when the relative humidity reaches a predetermined definite ratio.

3. A psychrcmetric instrument, comprisin dry bulb and Wet bulb thermometers, a switch controlled by each of said thermometers, a series of contacts engaged-by said switches, and a series of interchangeable members provided with conducting means for connecting contacts of one switch with contacts of another switch, to complete circuits between said contacts corresponding to various ratios of relative humidity.

4. A psychrometric instrument. comprising dry bulb and wet bulb thermometers, an electric circuit controlled thereby and ineluding a group of branches in parallel with each other, means controlled by said thermometers for completing the circuit through one of said branches according to the dry bulb and wet bulb temperatures, and means for varying the arrangement of said parallel branches to accommodate the instrument to any desired relative'humidity.

5. A psychrometric instrument, compris ing dry bulb and wet bulb thermometers, maximum? and minimum electric circuits controlled thereby and each including a group of branches in parallel with each other, means controlled by said thermometers for completing each of said circuits through one of its branches according to the dry bulb and wet bulb temperatures, and means for simultaneously varying the arrangement of the parallel branches of said two circuits to accommodate the instrument to any desired range of relative humidity.

In testimony whereof we hereby afiix our signatures.

EMIL J. CARROLL. GEORGE W. JOHNSON. 

